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clk: meson: add ROUND_CLOSEST to the pll driver

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Provide an option for the pll driver to round to the rate closest to the
requested rate, instead of systematically rounding down.

This may allow the provided rate to be closer to the requested rate when
rounding up is not an issue

Signed-off-by: Jerome Brunet <jbrunet@baylibre.com>
Signed-off-by: Neil Armstrong <narmstrong@baylibre.com>
This commit is contained in:
Jerome Brunet 2018-02-19 12:21:41 +01:00 committed by Neil Armstrong
parent c77de0e5c9
commit 0a1be867b9
2 changed files with 15 additions and 4 deletions
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17
drivers/clk/meson/clk-pll.c
View file

@ -105,7 +105,12 @@ static u16 __pll_params_with_frac(unsigned long rate,
u64 val = (u64)rate * pllt->n;
val <<= pllt->od + pllt->od2 + pllt->od3;
val = div_u64(val * frac_max, parent_rate);
if (pll->flags & CLK_MESON_PLL_ROUND_CLOSEST)
val = DIV_ROUND_CLOSEST_ULL(val * frac_max, parent_rate);
else
val = div_u64(val * frac_max, parent_rate);
val -= pllt->m * frac_max;
return min((u16)val, (u16)(frac_max - 1));
@ -125,9 +130,13 @@ meson_clk_get_pll_settings(unsigned long rate,
while (table[i].rate && table[i].rate <= rate)
i++;
/* Select the setting of the rounded down rate */
if (i != 0)
i--;
if (i != 0) {
if (MESON_PARM_APPLICABLE(&pll->frac) ||
!(pll->flags & CLK_MESON_PLL_ROUND_CLOSEST) ||
(abs(rate - table[i - 1].rate) <
abs(rate - table[i].rate)))
i--;
}
return (struct pll_rate_table *)&table[i];
}

2
drivers/clk/meson/clkc.h
View file

@ -71,6 +71,8 @@ struct pll_rate_table {
.od = (_od), \
}
#define CLK_MESON_PLL_ROUND_CLOSEST BIT(0)
struct meson_clk_pll_data {
struct parm m;
struct parm n;